Vehicle headlighting system



Marc-:h 22, 1949. IGRIFFITHS ET AL 2,465,085

VEHICLE HEADLIGHTING SYSTEM Filed May 15, 1948 lllll Invenof': Leonard Grifiths, George Edward Fadon, bg 4MM C;

Then ATOVTweH Patented Mar. 22, 1949 UNITED S TAT ES PATENT OF F IC E VEHICLE vHEADLIGrHTIN(Si SYSTEM' Leonard Griffiths-and George- 'Edward' Fardon,

Coventry, England,'assignors toGeneral Electric .'Company, a corporation of .N ewv York Applicationrliiay l5, 1948,. Serial No. 27,327 In Great. Britain September 11947"V 4- Claims.

This i invention relates to lighting systems and beamfof Alight and a' dip filament for giving a" deflected beam of light. This type of' lamp is generally suppliedl` with current from an alternetting-"current vgenerator of the type providing a substantially constant current under xed load conditions overa range of speed generally varying between 1000 to 5000 engine R. P. M. Under operating conditions of this type, when switching from the main filament to the dip filament of the headlight, and vice versa, an appreciable length of time elapses before the filament current builds up to normal value. This time lag is due to the initial low resistance of the cold filament and results in a momentary but appreciable blackout or diminution of the lamp illumination intensity. This objection cannot readily be overcome by modifying the design of the generator without impairing the constant current regulation cha-racteristic.

An object of our invention is to provide new and improved lighting circuits for headlights of vehicles supplied from alternating current generators.

Another object of our invention is to provide new and improved circuits for dual filament headlights for motor vehicles supplied from constant current variable speed alternating current generators which will eliminate variations in illumination intensity when switching from one lament to the other.

A further object of our invention is to provide means for connecting the filaments of a dual lamentary lamp in series to an alternatingr current generator or source of supply for headlight illumination and for short-circuiting as distinct from open-circuiting the filament circuit of the lamp not required.

Further features and advantages of our invention will appear from the following description of species thereof. For a better understanding of our invention reference may be had to the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawing, Fig. 1 illustrates diagrammatically the usual switching arrangement provided for a double filament headlamp; Fig. 2 illustrates diagrammatically a lighting system illustratingfa switching arrangement 'for a` double filament headlamp incorporating vour invention; and Fig; 3 illustrates a modification of Fig. 2 incorporating our invention.

Referring to Fig. 1, we havel there illustrated' a prior art lighting circuit to more clearly illustrate our invention, andv comprisingy a headlamp I-containing a pair of lamentsZ and 3 in series with acontrol switch 4 and a dipor selector switch 5 across an output circuit 6, 6 of a .substantiallyl constant-current variable-speed alternating current generator 'Il' Aresistance {llmayl beconnected across the output circuit 6, 6 of' the generator l through the control switch 4 to maintain a constant load when the head lamp illumination is not required. A rectifier 9 is connected in series with a battery I0 across the output circuit 6, 6 of generator I to provide unidirectional current for charging and maintaining battery I0 at full operating capacity. Switches II, I2 and I3 control the circuits of tail lamp I4, parking lamp I5, and horn I6 respectively.

When control switch 4 is closed to energize selector switch 5, either filament 2 or filament 3 is energized according to which of two positions a or b selector switch 5 occupies. 'Io energize the opposite filament, selector switch 5 is moved to the alternate position, thus open-circuiting the first-mentioned iilament. When changing selector switch 5 from position a to position b, or vice versa, an appreciable length of time elapses before the lament current builds up to its normal Value. This time lag is due to the initial low resistance of the cold filament and results in a momentary but appreciable blackout or diminution of the lamp illumination intensity.

In accordance with one aspect of our invention, as indicated in Fig. 2, the filaments 2 and 3 of headlamp I are connected in series with each other and with control switch 4 in a current supply circuit across the output circuit 6, 6. A pair of terminals 2' and 3' connect filaments 2 and 3 to the current supply circuit. Selector switch 5 of Fig. 1 is replaced with a make-and-break switch Il which is connected to a center tap or common terminal connection I8 between lilaments 2 and 3 and the ground connection of the output circuit B, 6'. When switch I'I is closed, filament 3 which may, for example, be the main beam lament, is shunted or short-circuited and the dip filament 2 alone is illuminated. When switch I'I is reopened, both filaments 2 and 3 are again in series. By this means the blackout is eliminated by having at all times filament 2 in the illumination circuitl conducting current. When control switch 4 is opened, breaking the illumination circuit, a compensating resistance 8 is inserted in the generator-circuit to retain the constant load condition.

Fig. 3 illustrates another variation of our invention containing the same constituent parts as Fig. 1 except that selector switch 5 is replaced with a two-positioned selector switch I9 which comprises a contact member 20 which, when in the position indicated in Fig. 3 across contacts 2|, 22 and with control switch 4 closed to energize lamp l, short-circuits filament 2, thus retaining filament 3 in the energized circuit. When control member 20 is moved to its other operating position across contacts 22, 23, it short-circuits lament 3, thus permitting filament 2 to remain in the energized circuit. During the transition period both filaments are connected in series, thus eliminating the possibility of a momentary objectionable blackout.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. In combination with an electric lamp comprising at least two serially connected filaments, a source of alternating current of substantially constant magnitude connected across said lamp, and means for short-circuiting at least one of said larnents without interrupting the current flow in another filament during operation of said lamp.

2. In combination with an electric lamp for a motor vehicle comprising at least two serially connected laments, a current supply circuit, a source of alternating current of substantially constant magnitude, a load resistance, a control switch for alternatively connecting said load resistance and said electric lamp in series with said current supply circuit, and means for short-circuiting at least one of said laments without interrupting 'the current ow in another filament during operation of said device.

3. In combination with an electric lamp for a. motor vehicle comprising a pair of serially connected filaments, a pair of terminals connected to the ends of said serially connected filaments, a common terminal connected between said serially connected filaments, a source of alternating current of substantially constant magnitude connected across said pair of terminals, and switching means connected to said common terminal for selectively short-circuiting one of said filaments.

4. In combination with an electric lamp for a motor vehicle comprising a pair of serially connected laments, a pair of terminals connected to the ends of said serially connected iilaments, a common terminal connected between said serially connected filaments, a source of alternating current of substantially constant magnitude connected across said pair of terminals, and a dualposition switching means comprising a contact member which is movable to selectively shortcircuit said common terminal and either one of the pair of said other terminals.

LEONARD GRIFFITHS. GEORGE EDWARD FARDON.

No references cited. 

